Lorne Basin, New South Wales: Evidence for a possible impact origin?
Titel:
Lorne Basin, New South Wales: Evidence for a possible impact origin?
Auteur:
Tonkin, P. C.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 45 (1998) nr. 5 pagina's 669-671
Jaar:
1998-10
Inhoud:
The Lorne Basin, situated on the north coast of New South Wales, is approximately circular in outline with its centre lying about 25 km southwest of Port Macquarie. It measures 35 × 30 km and is of Early Triassic age. There is some evidence to suggest that the Lorne Basin may have formed as the result of the impact of a large asteroid or meteorite, which probably measured 2-4 km in diameter. As well as the circular morphology and the presence of a central uplift possibly formed of impacted strata, there are a number of intrusive glass dykes in the Carboniferous age 'target' rocks underlying the basin. The glass contains small amounts of nickel-iron, iron-rich hypersthene and abundant spherules and melted fragments, and resembles the glass found at impact sites in other parts of the world. Following basin formation, thick beds of conglomerate, sandstone and shale of predominantly fluvial origin filled the basin, later subsidence possibly triggering the intrusion of a number of granitoids along impact-induced fractures. Phanerozoic cratering rates suggest that from 1 to 4 impact sites with a diameter of 20 km or greater should have formed in an area the size of New South Wales since the Cambrian, although none have yet been recognised.
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